Current studies on sucrose isomerase and biological isomaltulose production using sucrose isomerase

Isomaltulose is a natural isomer of sucrose. It is widely used as a functional sweetener with promising properties, including slower digestion, lower glycemic index, prolonged energy release, lower insulin reaction, and less cariogenicity. It has been approved as a safe sucrose substitute by the Food and Drug Administration of the US; Ministry of Health, Labor and Welfare of Japan; and the Commission of the European Communities. This article presents a review of recent studies on the properties, physiological effects, and food application of isomaltulose. In addition, the biochemical properties of sucrose isomerases producing isomaltulose are compared; the heterologous expression, fermentation optimization, structural determination, and catalysis mechanism of sucrose isomerase are reviewed; and the biotechnological production of isomaltulose from sucrose is summarized.     

Recent advances on physiological functions and biotechnological production of epilactose

Epilactose (4-O-β-d-galactopyranosyl-d-mannose), an epimer of lactose, is a rare disaccharide existing extremely small quantities in heat-treated milk, in which epilactose is produced by non-enzymatic catalysis from lactose. This disaccharide is a kind of non-digestible carbohydrate, has a good prebiotic effect, and promotes intestinal mineral absorption. This article presents a review of recent studies on epilactose formation in food system, qualitative and quantitative analysis, and its physiological functions. In addition, the biochemical properties and kinetic parameters of the epilactose-producing enzyme, cellobiose 2-epimerase, are compared, and the biotechnological production of epilactose from lactose is reviewed.     

酶法制备壳寡糖及其生物学功能

用正交试验方法考察温度、酶浓度、pH对蜗牛酶降解壳聚糖的影响,筛选蜗牛酶降解壳聚糖的最佳反应条件,采用SDS-PAGE方法分析降解产物,制备具有生物学功能的壳寡糖。用不同浓度的壳寡糖处理人肝癌HepG2细胞,观察细胞形态学变化,MTT法检测壳寡糖对其增殖的影响,琼脂糖凝胶电泳检测DNA变化,流式细胞术检测凋亡率(AR)。结果表明:蜗牛酶降解壳聚糖的产物主要是聚合度为4以上的寡糖,更多的接近壳六糖。最佳反应条件为pH 4.0、温度40℃、酶和底物质量比为4∶50;壳寡糖质量浓度在2~4 mg/mL时,对HepG2细胞增殖有抑制效应,细胞经壳寡糖处理48 h后,开始空泡化,DNA出现明显的凋亡条带,AR明显高于对照组。在最佳反应条件下蜗牛酶能较好地降解壳聚糖,制备的壳寡糖在一定浓度范围内能通过诱导HepG2细胞发生凋亡而抑制其增殖,其作用呈浓度依赖性。     

Continuous production of lactosucrose by immobilized Sterigmatomyces elviae mutant

In this study, in order to develop a continuous production process of lactosucrose in a packed-bed reactor, Sterigmatomyces elviae ATCC 18894 was selected and mutated. The mutant strain of S. elviae showed 54.3% higher lactosucrose production than the wild type. Reaction conditions such as temperature, pH, substrate concentration and flow rate were also optimized. Under optimized reaction conditions (50 degrees C, pH 6.0, 25% sucrose and 25% lactose as substrate, flow rate 1.2 ml/min), the maximum concentration of lactosucrose (192 g/l) was obtained. In a packed-bed reactor, continuous production of lactosucrose was performed using S. elviae mutant immobilized in calcium alginate, and about 180 g/l of lactosucrose production was achieved for 48 days.     

Recent research on the physiological functions,applications, and biotechnological production of d-allose

Applied Microbiology and Biotechnology - d-Allose is a rare monosaccharide, which rarely appears in the natural environment. d-Allose has an 80% sweetness relative to table sugar but is ultra-low...     

Karrikins信号传导通路及功能研究进展

Karrikins是从野火烟中发现的一类具有促进某些植物种子(如拟南芥、野燕麦)萌发的信号分子。自2004年其结构首次被解析以来,目前已经发现6种不同形式的Karrikin,其活性各有不同。虽然Karrikins被发现的时间较短,但其已成为植物分子生物学领域的研究热点。研究发现,Karrikins除促进种子萌发以外,还具有调控植物光形态建成、叶片发生等过程等生物学功能;此外,Karrikins与植物激素独脚金内酯(Strigolactone)在结构、信号传导通路等方面具有非常高的相似性。本文从Karrikins的发现史、信号传导通路、生物学功能及生态学意义等方面综述了其最新的研究进展,并探讨了Karrikins领域未来的研究方向。     

兼性厌氧细菌硫化氢的产生机理及其生理功能

硫化氢(H_2S)是继一氧化氮(NO)和一氧化碳(CO)后发现的第3种气态信号分子,但其细菌生理学研究才刚刚起步。本文根据作者对奥内达希瓦氏菌的研究,结合新近文献,就细菌的H_2S产生机理及其生理功能作了较为全面的阐述。细菌的H_2S产生途径主要有2条,一是通过降解半胱氨酸产生,二是通过厌氧呼吸产生。产生的H_2S除可为互生性微生物提供能源、供氢体和无机矿质营养外,还具有抑制竞争性微生物的生长,有效占领生态位的作用。H_2S在氧化应答中也起着重要的作用,一方面可抑制过氧化氢酶活性,增加过氧化氢对细菌的杀灭效果;另一方面可作为信号分子激活细菌的氧化应答,诱导拮抗系统的表达,保护细胞免受氧化损伤。这两种看似"矛盾"的作用与H_2S的处理时间有关:短时间处理以抑制为主,而延长处理时间则以保护为主。细菌H_2S产生机理及生理功能的阐明可为硫元素生物地球化学循环规律的揭示和感染性病原细菌的控制提供有益的参考。     

Current advances in biological production of propionic acid

Propionic acid and its derivatives are considered “Generally Recognized As Safe” food additives and are generally used as an anti-microbial and anti-inflammatory agent, herbicide, and artificial flavor in diverse industrial applications. It is produced via biological pathways using Propionibacterium and some anaerobic bacteria. However, its commercial chemical synthesis from the petroleum-based feedstock is the conventional production process bit results in some environmental issues. Novel biological approaches using microorganisms and renewable biomass have attracted considerable recent attention due to economic advantages as well as great adaptation with the green technology. This review provides a comprehensive overview of important biotechnological aspects of propionic acid production using recent technologies such as employment of co-culture, genetic and metabolic engineering, immobilization technique and efficient bioreactor systems.     

低聚乳果糖酶法制备的研究进展

低聚乳果糖是一种新型功能性低聚糖,是双歧杆菌的有效增殖因子。本文主要介绍了低聚乳果糖国内外研究状况、产品类型、安全性;重点介绍低聚乳果糖酶法制备方法,微生物来源,现有酶的改造修饰,并对制约低聚乳果糖发展的瓶颈问题简单概述。     

Insight into the physiological functions of PDGF through genetic studies in mice

Genetic analyses in mice have contributed significantly to the understanding of the physiological functions of platelet-derived growth factors (PDGFs) and their receptors. Phenotypic analyses of gene knockouts of PDGF-A, PDGF-B, PDGF alpha-receptors (PDGFRalpha) and beta-receptors (PDGFRbeta) have shown that these ligands and receptors play major roles during embryonic development. Conditional and subtle mutations in the same genes and analysis of chimeric mice have provided additional information about the roles of these genes in postnatal development. Transgenic over-expression studies have also demonstrated that PDGF ligands are capable of inducing pathological cell proliferation in a number of different organs. The present review summarizes these findings and discusses their implications for mammalian development and disease.     

钙网蛋白的生理及病理生理学作用

钙网蛋白（calreticulin,CRT）是内质网／肌浆网主要的Ca2^＋结合蛋白,通过协助蛋白质正确折叠和维持细胞Ca^2＋稳态而参与调节细胞凋亡、黏附、类固醇敏感性基因表达和自身免疫反应等,并与多种人类疾病的发生、发展和预后相关。本文综述钙网蛋白的生理功能及其在心肌肥大与衰竭、血管新生和应激等病理状态下的变化。     

Ageing and physiological functions.

In youth, most physiological functions have generous spare capacity. Even in health, however, increasing age is characterized by progressive erosion of these ''safety margins''. Examples include the decline of bone mass (towards a threshold for likelihood of fracture), of glomerular filtration rate (towards a threshold for susceptibility to clinical renal failure), of renal tubular function (towards a threshold for clinically important susceptibility to dehydration), of hepatic function (towards a threshold for accumulation following conventional ''young adult'' doses of common medications), or of lower limb explosive power (towards thresholds for impaired functional mobility). Increasing age is also characterized by a rising prevalence of chronic pathologies, complicating attempts to determine the rate or the mechanism of the age-related decline in a physiological function. Nevertheless, it is clear that in many organs the loss of function is largely attributable to the loss of functioning cells, even in the absence of overt disease. This apparently fundamental aspect of ageing remains poorly understood.     

Large scale production of glucose oligomers and polymers for physiological studies in humans

Methods for isolating relatively large quantities of glucose oligomer and polymer subfractions from a partial corn starch hydrolysate (PCSH) are described. To ensure that the products are suitable for physiological studies in humans, potentially toxic substances were excluded from the preparative processes. For long chain glucose polymer fractions with degrees of polymerization (DP) averaging 43 glucose units, we employed molecular filtration through Amicon YM5 membranes. For fractions containing glucose oligomers with DP's 3 through 8, we employed yeast fermentation followed by ethanol fractionation.     

Physiological problems of biological evolution. "Errors" in the development of physiological functions

During the evolution the physiological functions grow more perfect and complex. However, sometimes a developing function can show some evidence of regress and in certain cases can become the cause of dangerous diseases. The autoimmune diseases are among them. We conventionally call such cases the "error" of the evolution. In this work a negative role of leukocytes in the brain microcirculation is considered. With the help of experimental studies it was shown that leukocytes owing to their large volume (by a factor of 2-2.5 greater than the volume of an erythrocyte) slow down the capillary blood flow. As the result of the increasing tendency to adhesion, under the influence of hypoxia they make leukocyte conglomerates which cause the occlusion of venules and smallest veins of the brain. This is the reason for the known effect "no reflow" and results in an organism death.     

Current good manufacturing practice in plant automation of biological production processes

The production of biologicals is subject to strict governmental regulations. These are drawn up in current good manufacturing practices (cGMP), a.o. by the U.S. Food and Drug Administration. To implement cGMP in a production facility, plant automation becomes an essential tool. For this purpose Manufacturing Execution Systems (MES) have been developed that control all operations inside a production facility. The introduction of these recipe-driven control systems that follow ISA S88 standards for batch processes has made it possible to implement cGMP regulations in the control strategy of biological production processes. Next to this, an MES offers additional features such as stock management, planning and routing tools, process-dependent control, implementation of software sensors and predictive models, application of historical data and on-line statistical techniques for trend analysis and detection of instrumentation failures. This paper focuses on the development of new production strategies in which cGMP guidelines are an essential part.